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On an unnamed planet, a race called the Gonds are subject to the mysterious Krotons, unseen beings to whom they provide their brightest intelligences as “companions”. Thara, son of the Gond leader Selris, is the only one of his race to object to this practice. The Doctor, Jamie and Zoe arrive in time to witness the death of one of the chosen companions and intervene to save Vana, the other selected for this fate, using her survival as a means to convince Selris and the Gonds of the malign influence of the Krotons on their society. The Doctor calls it "self-perpetuating slavery” by which the brightest in Gond society have been removed. Similarly, there are large gaps in their knowledge, especially relating to chemistry. This situation has been in existence for many years since the Krotons arrived in their spaceship, polluting the lands beyond the Gond city and killing much of the Gond population.

Thara uses the disquiet of the situation to lead a rebellion and attack the Teaching Machines of the Krotons in the Hall of Learning. This prompts a crystalline probe to appear and defend the Machines, and warn the Gonds to cease their rebellion. Zoe now tries the Teaching Machines and is selected to be a “companion” of the Krotons. The Doctor elects the same fate and both are summoned into the Dynotrope where they are subjected to a mental attack. Zoe deduces that the Krotons have found a way to transfer mental power into pure energy, while the Doctor busies himself with taking chemical samples of the Kroton environment. Circumstances now trigger the creation of two Krotons from chemical vats within the Dynatrope (the Kroton spaceship). The newly created Krotons capture Jamie but are really seeking the Doctor and Zoe, the “High Brains”, who have now left the Dynatrope. It takes Jamie quite some time before he is able to make an effective escape.

Eelek and Axus, two councillors previously loyal to the Krotons, who begin to rally for all-out war with the Krotons, have now seized the initiative in Gond society. The more level headed Selris is deposed, but warns that an all-out attack will not benefit his people. Instead he has decided to attack the machine from underneath by destabilising its very foundation in the underhall. Eelek has Selris arrested and also reasserts control by negotiating with the Krotons that they will leave the planet if provided with the two “High Brains” who can help them power and pilot their ship. Zoe and the Doctor are forced into the Dynatrope and Selris dies providing them with a phial of acid which the Doctor adds to the Kroton vats. Outside, Jamie and the scientist Beta launch an attack on the structure of the ship using sulphuric acid. This two pronged assault destroys the tellurium-based Krotons and their craft. The Dynatrope dissolves away and the Gonds are free at last - choosing Thara rather than the cowardly and ambitious Eelek to lead them.

Holmes had originally submitted The Trap to the BBC as a stand-alone science-fiction serial in 1965. Head of Serials Shaun Sutton rejected the serial as being not the kind of thing the BBC was interested in making at the time, but suggested the writer pitch it to the Doctor Who production office as an idea for that series. Holmes did so, and although story editor Donald Tosh was interested, the scripts went no further at the time.

Some years later, assistant script editor Terrance Dicks found the story in the production office files when clearing a backlog, and decided to develop it with Holmes as a personal project, in case other scripts fell through. When the latter event occurred, Dick Sharples script Prison in Space a comedic dystopian tale where females rule with dollybird guards proved unworkable, Dicks was able to present the serial to his superiors as a ready production. Director David Maloney agreed the serial was viable, and it went before the cameras very quickly as an emergency replacement.

Several scenes were filmed at the Tank Quarry and West of England Quarry on the Malvern Hills.[4][5]

Cast notes

Broadcast and reception

The serial was repeated on BBC2 in November 1981, daily (Monday–Thursday, 9–12 November 1981) at 5:40 pm as part of "The Five Faces of Doctor Who", a series of repeats to bridge the long gap between seasons 18 and 19. At the time it was the only four part Patrick Troughton serial in the BBC archive.

VHS, CD and DVD releases

Episode One of The Krotons exists as both a 16 mm film print and a 35 mm telerecording negative. Clips taken from a VidFIREd transfer of the high quality 35 mm negative can be seen in the restoration documentary on the DVD release of The Aztecs and as part of the 40th Anniversary music video on Doctor Who DVDs released in 2003.